Dual functional porous organic polymer: Reversible iodine capture and selective sensing of picric acid

Abstract

The development of porous organic materials for removing radiotoxic iodine from nuclear plant waste is significantly relevant to environmental remediation as well as the detection of trace amounts of nitroexplosive picric acid for environmental safety is challenging. To achieve reversible iodine adsorption by the porous material, we have synthesized a highly stable porous organic polymer POF-1 by Schiff base condensation of tris(4-aminophenyl)methane and 2,2′-bithiophene-5,5′-dicarbaxaldehyde under microwave irradiation. POF-1 showed high affinity towards iodine adsorption due to electron-rich sulfur and nitrogen atoms in the porous structure which interact with iodine and form polyiodide ions by electrostatic interactions. POF-1 showed a remarkable iodine uptake capacity of 4.25 g g−1 in the vapor phase and could efficiently remove iodine from an iodine-cyclohexane solution with an adsorption efficiency of 141.0 mg/L. The iodine adsorption follows Langmuir's isothermal model i.e. monolayer adsorption and Pseudo second-order kinetics. POF-1 exhibited good recyclability towards reversible iodine capture even after five cycles. Furthermore, the luminescence characteristic of POF-1 has been employed for the selective detection of picric acid with high sensitivity with a detection limit of 8 μM among a range of nitroaromatic. The Fluorescence quenching mechanism is mainly attributed to photo-induced electron transfer and the inner filter effect.